Respiratory physiology is the study of how the body takes in oxygen and expels carbon dioxide. This process begins when air enters the lungs through the trachea and travels to smaller airways called bronchi and bronchioles. In the lungs, oxygen from the air passes into the blood through tiny air sacs called alveoli, while carbon dioxide moves from the blood into the alveoli to be exhaled. The respiratory system works closely with the circulatory system to deliver oxygen to cells and remove waste gases. Breathing is controlled by the diaphragm and other muscles, which expand and contract the chest cavity, allowing air to flow in and out. Proper respiratory function is essential for maintaining the body's overall health.